1. Field of the Invention
This invention relates to butterfly valves and particularly to butterfly valves as utilized for controlling the flow of fluids through three ports.
2. Description of the Prior Art
Butterfly valves having disc-shaped butterfly valve plates rotatable about an axis in the bore of the valve body are generally known in the prior art. Valves of this general description are employed in a variety of applications because of their straight flow-through construction and their excellent dirt handling characteristics.
In controlling the flow of fluids as in automotive heater systems coupled with air conditioning systems, it is common to shut off the flow of fluid to the heater core by means of a butterfly valve when the air conditioning system is in the maximum air conditioning mode. This permits the cold air from the air conditioner to pass through the heater core without transferring any heat from the heater to the cold air and thence directly to the passenger compartment. It is also common for liquid cooled internal combustion engines to be provided with a liquid bypass ahead of the heater shut-off valve to return liquid to the water pump when the engine block thermostat is closed to assist in the rapid warm-up of the engine block and associated components.
It has also been found desirable to restrict the flow of fluid to the heater core in order to protect it from excessive fluid pressure developed by the engine water pump at certain engine speeds.
U.S. Pat. No. 1,992,789 discloses a pivotally mounted butterfly valve which regulates the flow of fluid as in automotive heater systems. This valve has three ports. However, the butterfly valve is located such as to regulate the flow through only one port. Furthermore, the valve does not attempt to protect the heater core from excessive fluid pressure developed by the engine water pump.
U.S. Pat. No. 2,610,798 discloses a three way butterfly valve wherein the valve body is made from a "T" section fitting. A cup-shaped valve seat is secured to the main body of the "T" section fitting near the upright portion of the "T" section fitting. The valve seat carries a valve disc pivotally mounted thereon and adapted for movement between a first position closing an aperture formed in the valve seat and a second position in which the valve disc covers the open end of the upright portion of the "T" section fitting. This valve design does not protect the heater core from excessive fluid pressure developed by the engine water pump.
Neither of the above cited valve designs considered the possibility of eliminating the commonly used engine water bypass ports in the engine block with the attendant reduction in complications of small hoses and clamps. Furthermore, neither prior art design addressed the problem of leakage around the periphery of the valve disc and the need for virtually no leakage through the valve, as in automobile heating systems with air conditioning systems.